draft-ietf-bfd-rfc5884-clarifications-02.txt   draft-ietf-bfd-rfc5884-clarifications-03.txt 
Internet Engineering Task Force V. Govindan Internet Engineering Task Force V. Govindan
Internet-Draft K. Rajaraman Internet-Draft K. Rajaraman
Updates: 5884 (if approved) Cisco Systems Updates: 5884 (if approved) Cisco Systems
Intended status: Standards Track G. Mirsky Intended status: Standards Track G. Mirsky
Expires: December 18, 2015 Ericsson Expires: April 5, 2016 Ericsson
N. Akiya N. Akiya
Big Switch Networks Big Switch Networks
S. Aldrin S. Aldrin
Google Google
June 16, 2015 October 3, 2015
Clarifications to RFC 5884 Clarifications to RFC 5884
draft-ietf-bfd-rfc5884-clarifications-02 draft-ietf-bfd-rfc5884-clarifications-03
Abstract Abstract
This document clarifies the procedures for establishing, maintaining This document clarifies the procedures for establishing, maintaining
and removing multiple, concurrent BFD sessions for a given <MPLS LSP, and removing multiple, concurrent BFD sessions for a given <MPLS LSP,
FEC> described in RFC5884. FEC> described in RFC5884.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 18, 2015. This Internet-Draft will expire on April 5, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Table of Contents Table of Contents
1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 3 2. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 3
2.1. Procedures for establishment of multiple BFD sessions . . 3 2.1. Procedures for establishment of multiple BFD sessions . . 3
2.2. Procedures for maintenance of multiple BFD sessions . . . 4 2.2. Procedures for maintenance of multiple BFD sessions . . . 4
2.3. Procedures for removing BFD sessions at the egress LSR . 4 2.3. Procedures for removing BFD sessions at the egress LSR . 4
2.4. Changing discriminators for a BFD session . . . . . . . . 4 2.4. Changing discriminators for a BFD session . . . . . . . . 4
3. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 5 3. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 5
4. Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. Normative References . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Background 1. Background
[RFC5884] defines the procedures to bootstrap and maintain BFD [RFC5884] defines the procedures to bootstrap and maintain BFD
sessions for a <MPLS FEC, LSP> using LSP ping. While Section 4 of sessions for a <MPLS FEC, LSP> using LSP ping. While Section 4 of
[RFC5884] specifies that multiple BFD sessions can be established for [RFC5884] specifies that multiple BFD sessions can be established for
a <MPLS FEC, LSP> tuple, the procedures to bootstrap and maintain a <MPLS FEC, LSP> tuple, the procedures to bootstrap and maintain
multiple BFD sessions concurrently over a <MPLS FEC, LSP> are not multiple BFD sessions concurrently over a <MPLS FEC, LSP> are not
clearly specified. Additionally, the procedures of removing BFD clearly specified. Additionally, the procedures of removing BFD
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
2. Theory of Operation 2. Theory of Operation
2.1. Procedures for establishment of multiple BFD sessions 2.1. Procedures for establishment of multiple BFD sessions
Section 6 of [RFC5884] specifies the procedure for bootstrapping BFD Section 4 of [RFC5884] specifies the procedure for bootstrapping BFD
sessions using LSP ping. It further states that a BFD session SHOULD sessions using LSP ping. It further states that "a BFD session
be established for each alternate path that is discovered. This SHOULD be established for each alternate path that is discovered".
requirement has been the source of some ambiguity as the procedures This requirement has been the source of some ambiguity as the
of establishing concurrent, multiple sessions have not been procedures of establishing concurrent, multiple sessions have not
explicitly specified. This ambiguity can also be attributed in part been explicitly specified. This ambiguity can also be attributed in
to the text in Section 7 of [RFC5884] forbidding either end to change part to the text in Section 7 of [RFC5884] forbidding either end to
local discriminator values in BFD control packets after the session change local discriminator values in BFD control packets after the
reaches the UP state. The following procedures are described to session reaches the UP state. The following procedures are described
clarify the ambiguity based on the interpretation of the authors's to clarify the ambiguity based on the interpretation of the authors's
reading of the referenced sections: reading of the referenced sections:
At the ingress LSR: At the ingress LSR:
MPLS LSP ping can be used to bootstrap multiple BFD sessions for a MPLS LSP ping can be used to bootstrap multiple BFD sessions for a
given <MPLS FEC, LSP>. Each LSP ping MUST carry a different given <MPLS FEC, LSP>. Each LSP ping MUST carry a different
discriminator value in the BFD discriminator TLV [RFC4379]. discriminator value in the BFD discriminator TLV [RFC4379].
The egress LSR needs to perform the following: The egress LSR needs to perform the following:
If the validation of the FEC in the MPLS Echo request message If the validation of the FEC in the MPLS Echo request message
succeeds, check the discriminator specified in the BFD succeeds, check the discriminator specified in the BFD
discriminator TLV of the MPLS Echo request. If there is no local discriminator TLV of the MPLS Echo request. If there is no local
session that corresponds to the discriminator (remote) received in session that corresponds to the (remote) discriminator received in
the MPLS Echo request, a new session is bootstrapped and a local the MPLS Echo request, a new session is bootstrapped and a local
discriminator is allocated. The validation of a FEC is a discriminator is allocated. The validation of a FEC is a
necessary condition to be satisfied to create a new BFD session at necessary condition to be satisfied to create a new BFD session at
the egress LSR. However, the policy or procedure if any, to be the egress LSR. However, the policy or procedure if any, to be
applied by the egress LSR before allowing a new BFD session to be applied by the egress LSR before allowing a new BFD session to be
created is outside the scope of this document. Such policies or created is outside the scope of this document. Such policies or
procedures could consider availability of system resources before procedures could consider availability of system resources before
allowing a session to be created. When the egress LSR disallows allowing a session to be created. When the egress LSR disallows
the creation of a BFD session due to policy, it MUST drop the MPLS the creation of a BFD session due to policy, it MUST drop the MPLS
Echo request message. Echo request message.
Ensure the uniqueness of the <MPLS FEC, LSP, Remote Ensure the uniqueness of the <MPLS FEC, LSP, Remote
Discriminiator> tuple. Discriminiator> tuple.
The remaining procedures of session establishment are as specified Except for the clarification mentioned above, the remaining
in [RFC5884]. procedures ofBFD session establishment are as specified in
Sections 4-6 of [RFC5884].
2.2. Procedures for maintenance of multiple BFD sessions 2.2. Procedures for maintenance of multiple BFD sessions
Both the ingress LSR and egress LSR use the YourDiscriminator of the Both the ingress LSR and egress LSR use the YourDiscriminator of the
received BFD packet to demultiplex BFD sessions. received BFD packet to demultiplex BFD sessions.
2.3. Procedures for removing BFD sessions at the egress LSR 2.3. Procedures for removing BFD sessions at the egress LSR
[RFC5884] does not specify an explicit procedure for deleting BFD [RFC5884] does not specify an explicit procedure for deleting BFD
sessions. The procedure for removing a BFD session established by an sessions. The procedure for removing a BFD session established by an
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The procedures clarified by this document are fully backward The procedures clarified by this document are fully backward
compatible with an existing implementation of [RFC5884]. While the compatible with an existing implementation of [RFC5884]. While the
capability to bootstrap and maintain multiple BFD sessions may not be capability to bootstrap and maintain multiple BFD sessions may not be
present in current implementations, the procedures outlined by this present in current implementations, the procedures outlined by this
document can be implemented as a software upgrade without affecting document can be implemented as a software upgrade without affecting
existing sessions. In particular, the egress LSR needs to support existing sessions. In particular, the egress LSR needs to support
multiple BFD sessions per <MPLS FEC, LSP> before the ingress LSR is multiple BFD sessions per <MPLS FEC, LSP> before the ingress LSR is
upgraded. upgraded.
4. Encapsulation 4. Security Considerations
The encapsulation of BFD packets are the same as specified by
[RFC5884].
5. Security Considerations
This document clarifies the mechanism to bootstrap multiple BFD This document clarifies the mechanism to bootstrap multiple BFD
sessions per <MPLS FEC, LSP>. BFD sessions, naturally, use system sessions per <MPLS FEC, LSP>. BFD sessions, naturally, use system
and network resources. More BFD sessions means more resources will and network resources. More BFD sessions means more resources will
be used. It is highly important to ensure only minimum number of BFD be used. It is highly important to ensure only minimum number of BFD
sessions are provisioned per FEC, and bootstrapped BFD sessions are sessions are provisioned per FEC, and bootstrapped BFD sessions are
properly deleted when no longer required. Additionally security properly deleted when no longer required. Additionally security
measures described in [RFC4379] and [RFC5884] are to be followed. measures described in [RFC4379] and [RFC5884] are to be followed.
6. IANA Considerations 5. IANA Considerations
This document does not make any requests to IANA. This document does not make any requests to IANA.
7. Acknowledgements 6. Acknowledgements
The authors would like to thank Marc Binderberger for performing The authors would like to thank Marc Binderberger for performing
thorough reviews and providing valuable suggestions. thorough reviews and providing valuable suggestions.
The authors would like to thank Mudigonda Mallik, Rajaguru Veluchamy The authors would like to thank Mudigonda Mallik, Rajaguru Veluchamy
and Carlos Pignataro of Cisco Systems for their review comments. and Carlos Pignataro of Cisco Systems for their review comments.
8. Normative References 7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol [RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379, Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006. DOI 10.17487/RFC4379, February 2006,
<http://www.rfc-editor.org/info/rfc4379>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010. (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<http://www.rfc-editor.org/info/rfc5880>.
[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"Bidirectional Forwarding Detection (BFD) for MPLS Label "Bidirectional Forwarding Detection (BFD) for MPLS Label
Switched Paths (LSPs)", RFC 5884, June 2010. Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
June 2010, <http://www.rfc-editor.org/info/rfc5884>.
Authors' Addresses Authors' Addresses
Vengada Prasad Govindan Vengada Prasad Govindan
Cisco Systems Cisco Systems
Email: venggovi@cisco.com Email: venggovi@cisco.com
Kalyani Rajaraman Kalyani Rajaraman
Cisco Systems Cisco Systems
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